1. Field of the Invention
The methods and apparatus 100, 200, 300 described herein relate to the field of analyte detection and/or identification. In particular, the disclosed methods and apparatus 100, 200, 300 relate to the use of feedback-controlled cantilever 110, 210, 310, 400, 510 deflection for analyte detection and/or identification.
2. Related Art
Various methods have been used for detection and/or identification of biomolecule analytes, such as proteins, peptides, receptors, nucleic acids, hormones, metabolites, etc. Antibody based assays have been used to detect and/or identify a large number of analytes. Any compound, composition, molecule or aggregate for which a specific binding antibody can be made may be detected by a variety of immunoassay techniques, such as ELISA, Western blotting, etc. In general, either the analyte (antigen) of interest, or an antibody against the analyte of interest, is attached to a solid support. If the analyte is bound to the support, an antibody that binds to the analyte may be labeled with a fluorescent, enzymatic or other label and attachment of the antibody to the bound analyte may be detected. If a first antibody is bound to the support, binding of analyte to the first antibody may be detected by binding of a second, labeled antibody to the analyte (sandwich assay). Antibody based assays may occasionally show unacceptably high levels of false positive or false negative results, due to cross-reactivity of the antibody with different antigens, low antigenicity of the target analyte (leading to low sensitivity of the assay), non-specific binding of antibody to various surfaces, etc.
Oligonucleotide hybridization based assays are in wide use for detection of target oligonucleotides, messenger ribonucleic acids (mRNAs), genomic deoxyribonucleic acid (DNA), etc. In such assays, a probe oligonucleotide that is complementary in sequence to a nucleic acid target analyte is labeled and allowed to hybridize to a sample suspected of containing the target nucleic acid. Many variations on this technique are known, such as Southern blotting, dot-blotting or slot-blotting. More recently, DNA chips have been designed that can contain hundreds or even thousands of individual oligonucleotide probes. Hybridization of a target nucleic acid to a probe oligonucleotide may be detected using fluorescent labels, radioactivity, etc. Problems with sensitivity and/or specificity of such assays may arise. Nucleic acid hybridization may occur between sequences that are not precisely complementary through mismatch hybridization, leading to false positive results.
Other types of analyte detection assays are known, such as enzyme activity assays, receptor-ligand binding assays, etc. As with the techniques discussed above, selectivity and/or sensitivity problems may arise with any standard detection technique. A need exists in the field for selective, highly sensitive methods of detecting and/or identifying various analytes.